This project uses established cellular models in culture to examine molecular event which account for the acute effect of ethanol and the development of "tolerance" and "dependence" at a cellular level. Our laboratory has shown that acute ethanol in serum-free defined medium produces increases in cAMP levels in NG108-15 neural cells and S49 lymphoma cells whereas chronic exposure to ethanol causes a heterologous desensitization of adenosine and PGE1 receptor-coupled cAMP production in the same cells. We have discovered that ethanol induced accumulation of extracellular adenosine is required for these changes and this proposal examines the role of adenosine in mediation these responses. Adenosine transport, extracellular adenosine concentration adenosine receptors, intracellular cAMP levels and cAMP-dependent protein kinase activity will be measured during acute and chronic exposure to ethanol to determine the concentration of ethanol and the time of exposure required to produce the chronic responses to ethanol. The role of cAMP in the acute and chronic effects of ethanol will be determined using S49 wild type and mutant cells which lack specific components in the cAMP signal transduction pathway. Studies of alcohol withdrawal will determine which mechanisms are altered as cells return to normal function. This project will determine whether acute ethanol induced changes in cAMP (as a result of adenosine receptor activation) and PKA are responsible for the chronic effects of ethanol or whether alternate adenosine receptor dependent events are involved. We have discovered that lymphocytes from alcoholics exhibit a four fold reduction in receptor dependent cAMP levels which appears to have pathophysiologic significance. We can determine the mechanisms responsible for these changes by studying cell lines in culture. This may make it possible to select specific pharmacologic agents to prevent the development of alcohol dependence.